Roofing types for NZ residential jobs

Roofing is a system, not just a sheet: pitch, profile, underlay and flashing all have to work together for the roof to shed water and last. This is a quick reference to the roofing types you’ll meet on NZ residential jobs, and the minimum pitch and spec that govern each one. For metal roofing, the NZ Metal Roof and Wall Cladding Code of Practice is mandatory companion reading.

Long-run metal

The workhorse of NZ residential roofing — light, cost-effective and available in long sheets. The profile you pick sets the minimum pitch you can lay it at.

• Corrugate (Dimond Corrugate / Colorsteel) — 0.40mm Colorsteel Endura/Maxx or ZINCALUME, 8mm × 76mm profile. Minimum pitch ≥8° (1:7.1) for a normal lap, or ≥3° (1:19) with extra seal. The most common NZ residential roof, in sheets up to 16m.
• 5-rib trapezoidal (Dimond / Roofing Industries) — 0.40–0.55mm Colorsteel with a wider profile and deeper rib (~21mm). Minimum pitch ≥3° (1:19). A modern flat-ish look that’s better for low pitch, at slightly more cost.
• Standing seam (Dimond Metalcraft, Roofing Industries) — concealed-fix standing seam (Tray, Espan series). Minimum pitch ≥3°. Premium architectural look with no exposed screws.
• COLORCOTE® pre-painted aluminium — 0.7mm pre-painted aluminium. Minimum pitch ≥3°. Corrosion-immune, which makes it a coastal Zone D option, for more money.

Tile

Tile gives a traditional look and long life, but concrete and clay are heavy — the framing has to carry the weight, so check it before you commit.

• Concrete tile (Monier, Dimond) — pressed concrete at 25–30 kg/m² (heavy), typically 420×330mm. Minimum pitch ≥15° (less for special profiles). Traditional NZ look with 50+ year life, but needs upsized framing.
• Clay tile (Monier Marseille) — fired clay terracotta, heavier again than concrete. Minimum pitch ≥17°. A European/Mediterranean look that’s long-lived and colourfast.
• Pressed metal tile (Gerard, Decramastic, Metrotile) — 0.40mm steel pressed into a tile profile with a stone-chip coating. Minimum pitch ≥10°. The look of tile with the weight of metal, so lighter framing is OK.

Membrane and low-pitch

When the fall is too shallow for lapped sheets — flat decks, internal gutters, complex shapes — you go to a membrane system.

• Butynol (Ardex Butynol) — 1.5mm butyl rubber sheet, hot-air welded. Minimum fall ≥1.5° (1:38). Suits flat decks, internal gutters and lower-pitch sections, with 20yr+ life.
• TPO / EPDM — thermoplastic polyolefin or EPDM rubber sheet. Minimum pitch ≥1.5°. More common on commercial flat roofs, and residential decks sometimes.
• Liquid-applied (Equus, Viking) — polyurethane or acrylic applied wet and cured in place. Minimum pitch ≥1.5°. Good for decks, complex shapes and retrofits; reapplied every 10–20yr.

Other types you’ll see rarely

• Asphalt shingles (GAF, IKO bituminous) — minimum pitch ≥18°. Rare in NZ, more common in the US/Canada, and on North Shore character homes sometimes.
• Slate (natural or synthetic) — minimum pitch ≥25°. Heritage restoration only, and very expensive.

Re-roof: the corrosion-zone call

On a re-roof, the site’s corrosion zone drives the coating and fixings you can use — the closer to open coast, the tougher the spec. This is set out in NZS 3604 §4.4 and the MRM Code of Practice §4.5–4.6.

• Zone B (inland) — Colorsteel Endura.
• Zone C (500m–2km) — Maxx.
• Zone D (<500m open coast) — Maxx/Maxam or ZAM, with SS316 fixings and 0.7mm flashings.